Speculation about how long exactly a 'Winter' lasts in Westeros, partially substantiated from comments found in the books, tend to imply that the actual coming of Winter is pretty much random — i.e., Winters may be long or short, but it's safe to assume that they are at least 1-3 years long, but sometimes last a whole decade.

Now this raises a huge logistic problem. It's true that (at least in the books) people have a lot of warning that 'winter is coming' and therefore we see farmers trying to plant as much as possible, making sure they get a couple or more harvests in before winter truly sets in. So far, so good.

However, this is a fantasy/Middle Ages setting — at least on the Westeros side of the world; Braavos and the Free Cities seem to have developed a more sophisticated culture, but that's another story. This means that we ought only to have certain methods of preserving food for a long time. Out of my mind, the only way I see someone worrying about food stockage is Jon Snow, who explains that the storage of meat is done inside the Wall, which is always cold, and this would be a naturally obvious place to store food.

Nevertheless, no matter how cold the Wall might be, there is clearly a limit in how much it can store (the Wildlings soon deplete the cache held by Jon) and, of course, in its duration. In the real world we can deep-freeze meat for about a year. Let's stretch the point and believe that the Wall is able to keep it frozen for that long — after all, the Wall is certainly magical, and we know it's used as a freezer, so, ok, we can assume it's 'as good as our 21st century freezers'.

Fine. But if a Winter lasts a decade (and we know for sure that this is certainly possible), then where will be meat stored? It will spoil after a year. What will people eat then?

And of course this only applies to the Wall. Nowhere else is mentioned how food is preserved. We can therefore only presume that traditional methods for food preservation will be used. Curing, smoking, salting meat will preserve food for about a year as well, and assuming you have a whole industry able to process tons of meat for the whole population, then you could presumably survive the first year of winter without starving.

But this would assume that everybody has (relatively) cheap access to meat, which runs contrary to what a Middle Ages setting ought to be. Meat was an expensive commodity only available to the wealthy. It's not unlikely to find meat at the Wall — after all, they get it from donations and so forth — since meat would also be given to some of the soldiers, at least during the time that they would be active (in the Middle Ages, this would be little more than three months), although pillaging — which we know happens in Westeros as well — would be the best way of supplying armies with food (they would not need large baggage trains).

In other words: there is some consistency in the way food is produced in Westeros, and how the aristocracy, the peasants, and the armies are fed. Martin is clearly fond of food, since he describes it in such a minute detail. We get plenty of hints that farmers are truly able to plant a lot, and Westeros seems to be mostly very fertile (except perhaps in the far north, and, of course, in the Dorne deserts), so there is no problem in having plenty of food — even (apparently) during crushing wars, which destroy a lot of the plantations by permanent pillaging. Nevertheless, we see that most areas (and large cities) in Westeros continue to be reasonably well supplied with food. Westeros has lots of food. That makes sense during 'Summer' — in our own world, we have plenty of places where seasons are pretty much nonexistent and it is plausible to have multiple crops in a year.

So... we can safely establish that there is plenty to eat in Westeros. Now we just need to know what they eat during Winter!

One possibility, of course, is trade. In other words: because apparently only Westeros is seriously affected by Winter (Essos much less so), it's conceivable that, during Winter, Westeros would import food from the Free Cities. In fact, this could have been one of the reasons why Valyria didn't have a strong hold in Westeros before the Targaryens: it would be hard to keep everybody fed during Winter. So, let's assume that the Westerosi have solved this issue through trade — we know that trade is plenty and common among Westeros and Essos (and other further-away lands, but let's stick to those for a moment).

Ok, trade. But trade... what? Westeros seems to have only three kinds of possible exports: wine (Dorne), food (since it's so plentiful, it must be cheap during Summer), and gold (from the Lannisters). Food and wine, of course, cannot be traded during Winter — since, naturally enough, Westeros would be lacking both. They might sell a little wine at first (because wine can be bottled for much longer than a year, and it's conceivable that Dorne had acquired that knowledge from the times of Valyria — pretty much like we Europeans continued to plant wine after the fashion of the Romans, centuries after the Roman Empire collapsed), but, lacking the ability to replenish their stores, at some point — especially during very long Winters! — that supply would go out.

That means that what remains for trade is basically gold. Which, needlessly to say, is not a bad commodity to trade: it doesn't rot or spoil, it's compact, it's easy to store and to transport. And we can imagine — I have no reference, just wildly conjecturing — that possibly Valyria was not aware of the vast amount of gold under Westeros' crust, and somehow the Targaryens figured that they could survive the long Winters by mining gold and trading with the Free Cities. Of course, food prices would skyrocket during Winter, but they would be compensated after Winter, since Westeros is apparently able to produce quite a surplus of food (and wine!) during Summer. In those years, the trade routes would actually work in reverse — Westeros exporting food and getting gold in return. A good King would manage the economy so that it balances out without going bankrupt, and I think this would be manageable.

There are just two catches with this theory.

The first, of course, is that we know that the Free Cities are 'mostly wasteland' (except for the city-states themselves), and even if they are not exactly pictured as 'deserts' (like, say, the Green Sea), it's clear that whatever villages and townships that may have existed have long ago been razed to the ground by the Dothraki and their population fled to the safety of the nearest city walls. That means that all food for those cities must be imported as well. Again, this doesn't pose a problem — lots of civilizations flourished in our own Earth using ship trading to supply cities with food — but it means that, during Winter, even if Westeros is willing to pay well, and Winter does not affect the food production that already supplies the Free Cities, it would probably be too scarce anyway. In other words: during Winter, the Free Cities would hardly be able to feed themselves, never mind about selling any non-existing 'surplus' to Westeros. This clearly doesn't work.

So we need to speculate that, during Winter, there are much longer trade routes, to those continents of which we know so little, and food must be imported massively from there — to feed Westeros but also Essos. Again, we can also speculate that such extremely long trade routes only became possible thanks to an advance in naval technology only possible during a relatively peaceful period while Westeros was united under the Targaryens, and that in the times of the Valyrians such extensive trade routes would be unfeasible with existing technology (again, see the parallels between the Roman Empire and the Renaissance in our own Earth — while the Romans had an incredibly advanced naval fleet, and an astonishing amount of 'scientific' knowledge about navigation techniques and so forth, they were unable to 'escape' the Mediterranean (except for occasional ventures) — while during the Renaissance we were able to pretty much establish trade routes world-wide, in journeys that could take a year to complete, but which were highly profitable, to pay off the huge investments made in naval technology of the time — which was not cheap, and navigation knowledge was scarce, mostly a State secret, but... it still managed to give us extensively long trade routes).

This launches us into the second catch: if the above is true, then Westeros would be a major naval superpower. But we know this is not the case. It's true that each of the kingdoms do, indeed, possess relatively good fleets (some naturally in larger number than others) and that the merchant fleets are adequate for trade overseas with the Free Cities (at least those closer to Westeros...). But it seems that in terms of technology, clearly Braavos is the technological naval superpower of the age (like the Venetians shortly before Renaissance in our own world). And it makes sense, too: after all, as said, Braavos is a trading nation (and a financial one as well) and must import all its food as well (except for fish, of course), so it means tackling the issue of handling very long overseas trade routes. Braavos is also sufficiently to the north to feel the adverse issues of Winter (even if not at the same intensity as Westeros) and that might have pushed them to develop a more advanced naval technology than, say, other Free Cities.

Because Braavos — and not any city in Westeros — leads naval technology, we have therefore to assume that Westeros is not yet at the stage of being able to do long oversea journeys (or they would have quickly matched Braavos in technology, and Braavos would not be so important — naval-wise — as Martin makes us believe they are). This means they have to establish complex trading routes with lots of intermediaries, i.e. assuming that Free City 1 trades food with Free City 2, and so forth, until the most remote corners of the planet, while Westeros only bothers to trade with Free City 1. This kind of arrangement, again, is also very plausible: during the Renaissance, the Ottomans managed to connect the rich cities of Europe with the wealth-producing cities of the far East that way, and explored those trade routes commercially with huge success — until the Portuguese tricked them out... by navigating around Africa and competing with alternate trade routes... but that's another story: in Martin's world, it is conceivable that most trade happens in (relatively) short hops between the Free Cities in Essos and even with the other continents, while presumably Braavos has a better, more advanced naval technology, and might be able to do very long stretches of oversea voyages — meaning that they can cut the intermediaries, go directly to the source, buy much cheaper and get a much larger margin of profits, which would also explain very neatly their immense wealth.

The second catch is not only the necessity of developing naval technology to reach the furthest shores of Martin's planet; not even to mention that in our own history we rarely had such massive amounts of food being pushed across the oceans to feed so many people (it's a logistical nightmare); no, the problem is that during Winter, we know that the ocean — at least around Westeros and the western coast of Essos — becomes pretty much impossible to navigate, or at least so dangerous that it's not worth the cost (both in ships and human lives).

So, while this elegant theory of long supply chains of massive amounts of food over the oceans all around the four (or more) continents is a very neat, romantic idea — one that would explain Braavos wealth, but also the wealth of the other Free Cities, namely those that are huge ports and rely exclusively on food being supplied overseas — but, alas, it fails because Westeros is not reachable by sea during the Winter. One might conjecture that the seas further south, around Dorne, might be navigable during Winter, but then we have another problem: suppose that we do, indeed, use Dorne's ports to receive all the food to distribute around Westeros. What next? Take a look at the maps. Dorne is 'mostly desert'. Its major cities are near the sea or the vast rivers crossing the desert. So, yes, we might be able to supply Dorne by sea; but there are no roads to the North. Well, there are a few. But they don't lead to any seaport! (at least not to any mentioned in the maps)

Even so, picture the following scenario: galleys coming in to Dorne's seaports, vastly loaded with food (and we are talking mostly about preserved meat, of course; what else would survive long journeys across the oceans?). Picture the food for millions and millions of people. Now this food needs to be hauled over land routes, because all ports above a certain latitude will not be reachable during Winter. Imagine thousands upon thousands of ox carts and their drivers, crammed full with food, driving northwards across all roads... after crossing Dorne's deserts... and, as they drive further north, they will be subject to the harshness of Winter. And this needs to be done every day, for a whole decade, assuming a very long winter.

Does it seem practical to you? Or even feasible? Well, I could barely imagine that the Targaryens, especially if they had free access to all the Lannister gold, could conceivable organise such a vast and complex logistics operation... but we must forget that even Valyria with all its amazing, superior technology (or magic) were unable to do so.

So what is the secret of Westeros? What do they eat during the very long winters — and how do they manage to survive the Winter?

Some references to the Winter's length (as well as some explanations to mild variations among the 'year' and the ability to harvest often during the same year):

good god this wall of text.... I can't even. They probably the same types of things people in the real middle ages ate during winter.
– SkoobaJun 25 '16 at 13:29

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@Skooba Give him a little credit here, that's not a wall of text, that's research effort. I don't even watch the show and I learned more about Westeros and meat preservation in the Middle Ages than from any other two questions on this site.
– GGMGJun 25 '16 at 16:05

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I seriously think a good half (if not more) of this "question" could be moved into a proper answer; answering your own questions is perfectly legit.
– lfuriniJun 25 '16 at 16:57

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They rely on income from the TV and merchandising rights.
– Dan SheppardJun 25 '16 at 19:46

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This is an interesting essay, but it should be rewritten. First, generally it is a bit tortuous, and you should impose some more organization onto it. Start out by briefly enumerating the various possible sources of food in the beginning, then proceed to examine each one separately under its own sub-heading. Second, while the question is good, I think as written it fits a blog (like the xkcd blog) more than the site - I think you should drastically cut down the question to 2-3 paragraphs, and then submit your reasoning as your own answer.
– SuperbestJun 25 '16 at 22:12

4 Answers
4

Westeros can produce food during winter and many people probably don't survive

First of all: that was a long and detailed question, upvote for you. Now for the answer, it seems to me you are assuming two things:

Almost nothing grows in Westeros during Winter

Most people survive the winter.

About the first one, we know there are means to produce food during Winter, at least one method is Glass Gardens, in Winterfell they have one kept warm by hot springs:

The castle had been built over natural hot springs, and the scalding
waters rushed through its walls and chambers like blood through a man’s body, driving the chill from the stone halls, filling the glass gardens with a moist warmth, keeping the earth from freezing.

George R.R. Martin, A Game of Thrones

We can presume other ways are available specially in southern lands, were food can probably be produced even without hot springs (like Koca added some areas of Westeros are not hit so hard, and there are cold resistant crops). It's probable that hunting and fishing are still available (after all wild animals survive: not all the grass is frozen). We know that during a 6 years winter (130-135 AC) there was a succession war, probably not very good for trade and still troops could be sustained.

But then again food production is obviously abruptly decreased and, as you carefully pointed out, there are no means to efficiently trade food. Many people are not going to make it through the Winter, and that's why most people mention it with dread and it's a subject of terror stories

“Oh, my sweet summer child," Old Nan said quietly, "what do you know of fear?
Fear is for the winter, my little lord, when the snows fall a hundred feet
deep and the ice wind comes howling out of the north. Fear is for the long
night, when the sun hides its face for years at a time, and little children
are born and live and die all in darkness while the direwolves grow gaunt and
hungry, and the white walkers move through the woods”

+1 for the glass garden. I did not remember that :)
– C.KocaJun 25 '16 at 17:09

10

There are other possible sources of heat too - in Britain decomposing manure was used as a heat source to grow pineapples in the 19th century. Of course, this is not stated in canon, but people make poop whether its in the story or not.
– CriggieJun 25 '16 at 23:14

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@Cassius40k I think that's more of a poetic exageration, days grow shorter and it frequently snows.
– RamJun 26 '16 at 20:26

Excellent question, and an excellent answer, but I have a few things to add.

Storage:
Westerosi people are used to the long winters. They prepare for them. Baelish once said in the small council meeting:

We have enough grain for five years. If the winter lasts longer, we'll have fewer peasants.

What Baelish suggests is not unfamiliar to our world. India used to, maybe still does, get long drought of a few years. Pre-British Indian taxation system makes sure that a good amount of the current harvest is stored by the local feudal lords. British destroyed this system and the results were not pretty.

They do not only store grain but also meat. Contrary to what you suggest, salted meat in a cold environment can last for years. I was told Turkish Military had refrigerated salted meats from ten years. Although it lacks the flavor, it contains the nutrients.

Ice Fishing:
Although it is not very abundant, people do break the ice and fish.

Hunting:
It is again, not extremely abundant, but people do hunt in the winter.

Trading:
Westeros has some mines, most notably copper and iron mines. Timber is another important trade good. And, I guess White Harbor is accessible for most of the winter.

Animals:
Hay is very durable, and can be used to feed animals. Animals are also essential to provide heat, so every household in the North must have a few animals to survive the winter. (Consider Craster's Keep) These unfortunate animals convert hay into bacon.

Highgarden and Dorne:
Winter does not hit that hard to these places, so people may grow some crops that can sustain cold. Potatoes, onions and barley are cold resilient.

Jon planned to take all valuables of the freefolk and a loan from the Iron Bank to trade with Highgarden and Dorne.

Now that I completed this part, I will go on to Essos. Dothraki are not as savage as they seem. As Illyrio Mopatis suggests, most of the time, horde is persuaded by gifts. Besides, horde is usually not that big. Khal Drogo managed to unite most (maybe all) Dothrakis, but usually they are divided to smaller groups. There is a good chance they would not dare to raid areas close to big cities like Myr or Volantis. Essos has alternative food sources as well. We know that Ibbenese are whalers.

On-site production

I'm not sure if we've ever actually seen what the Westerosi winter looks like yet, but I'm assuming it's basically like a normal Earth winter, but longer. Presumably there is less sunlight (hence the cold). This would of course prevent plants from growing.

Crops

Things like greenhouses and hydroponics, while a bit anachronistic for the technological level in Westeros, are in principle possible. However we've seen no mention of them, and in any case I don't think it's feasible to produce a significant fraction of food this way. At best it might be a niche source of luxury fruits and vegetable for the wealthy (Wikipedia mentions just such instances).

However, there are other means of producing food that are less dependent on climate.

Hunting

Hunting probably wouldn't produce enough bulk calories, but is significant for filling a nutritional hole and providing a steady source of animal protein. The question is whether there would even be any animals to hunt with such a long winter (which brings up the question of what the wild animals eat).

Martin's conception of a multi-annual winter is a little bizarre in my opinion. If this has been going on a geological time scale (eg. millions of years) it would either create flora and fauna radically different from what we see here on Earth, while the novels seem to portray basically the same animals and plants we have, with the occasional exotic exception. On the other hand if this climate is recent (for instance a magical catastrophe a few centuries ago) the ecosystem would be devastated. So I think this is not an adequately supported element of the books, and we can't easily answer the question of whether there would be enough game.

Fishing

In addition, there is also fishing (and presumably whaling, which the books don't mention but historically has been practiced by many people since ancient times). However, again fish stocks are ultimately supported by algae in the ocean, and even if ocean temperatures can remain stable despite the winter, the reduction of solar energy would mean the algal stocks crash, and with them the fish stocks. The books give no indication that its marine ecosystems differ hugely from ours (what would the fish eat?), so we have no way of knowing if there's enough fish in the ocean at winter, but it's plausible as a major food source.

Livestock

Livestock, of course, is most easily farmed on pasture, which in the winter are gone. But much like in our world, the animals are still there. They can be kept in barns, fed feed or hay which has either been stockpiled earlier or is imported. In our world, farm animals tend to not reproduce much in the winter; the books do not say out how animal life cycles are affected by the longer seasons. Presumably the animals can be made to breed throughout the winter (which is biologically a little silly, but oh well), so if a source of feed is maintained, livestock can be propagated and consumed indefinitely.

Stockpiles

Of course when you have such long winters you would prepare for them. In fact those who fail to prepare would be strongly selected out - and the Westerosi people should at least have radically different time preference than us, both culturally and biologically (if you believe that psychology can have genetic components like this). However, the people in the books seem to behave basically like Earth humans... At any rate, even an Earth human, confronted with such a climate, would easily make the connection and keep a large stock of food.

The persistent low temperature already helps preserve food (although yet again, this climate, as well as the storage behavior of humans, and probably animals, should lead to the evolution of many more cold-tolerant microbes than on Earth that make food spoilage worse). There are relatively easy ways of preserving food for multiple years that were feasible even in pre-industrial times.

Grains

Seeds are already evolved to stay intact for many years. These can be stocked directly, or processed (eg. flour).

If you eat nothing but grains that long you'll get sick of it pretty fast, and you will have some serious malnutrition, but in theory you could survive (as countless peasants have for centuries). Hunting, fishing, trade and greenhouses could help reduce these problems.

Of course, the dietary shock is still there, and in Westerosi society there should be an obvious public health phenomenon where certain generations (such as children raised during winter) should be markedly different (in health, behavior, stature, physical condition, and number) than others - something which we have barely seen (there's the expression "summer child"). So once again, it's hard to speculate on how public health will be affected by this switch to stockpile vs. fresh food.

Regarding meat, you point out that it can be kept deep frozen for a year. However there are other ways of preserving meat. Even in pre-industrial times, human cultures developed many methods of smoking, drying and salting meat or fish to preserve it for long winters (4-8 months in the arctic), sea voyages (up to a year) and so on. Drying in particular is a very primitive method that can preserve meat for years, I'm sure the Westerosi would have discovered even more effective meat preservation methods than our primitive cultures, since they had a stronger impetus to do it in the form of long winters.

For instance, I would wonder if canning would be discovered early on such a world. Even in our history, it was invented (at first with glass jars) long before the microbiology involved was understood, so it's not a huge stretch. Of course, there is mysteriously no mention of canning in the books.

Trade

It isn't clear to me how prevalent the winter is outside Westeros. The continent is already pretty far up north, with permanently snowy areas like the area near the wall. The parts taking place in southern lands such as Qarth suggest the world is a spherical planet with an equator and sun resembling ours. Much like on our world, despite the winter there should be many parts of Essos that can produce food, and are a few weeks away by ship.

You have already discussed this quite a bit, so I'll just add some of my own points.

What do the Westerosi sell?

There are several exports Westeros has that you have not considered. Besides food, wine and gold, there is also timber (trees can be cut any time), iron and other metals (mines can work year-round), stones (such as marble, though rarely mentioned in the books), gems, finished goods of various sorts (all these farmers have no farming to do for years, so you'd think they'd become artisans of various sorts), textiles and clothing, ships, livestock, fish, processed food (again, while going against the books, if you follow my suggestion that canning is invented early in Westeros, they could import raw food or even live animals and export the cans or other preserved meat), medicines, books and many other things can be exported. Money can also be borrowed to finance the food imports.

Remember that there is a huge population of farmers, which now have nothing to do for years. This means you have an excess of labor, which can be used to fuel a wide array of cottage industries and turn Westeros into a manufacturing giant.

Market volatility and the length of trade routes

I disagree with the food price spikes. While indeed this multi-year seasonal cycle will warp the economy, ultimately the market is efficient. Traders would arbitrate away much of the supply/demand shocks, given how predictable the seasons are.

I'm not sure why you consider Essos a food importer. From what I recall, it is not made clear whether the Dothraki are actually an ever-present, all-destroying scourge on the continent or a minor nuisance. Of course when Dany lives among them, from her point of view they seem like great conquerors and raiders, but it is also clear that their tribal organizations are unstable and there don't seem to be that many of them. During the Dothraki chapters, we see many communities of people whose main activity appears to be agriculture (for instance the lamb-men), much of the continent is covered in vegetation (and so is presumably fertile). Even if indeed very long trade routes were necessary, such as going all the way to Qarth, Yi Ti, Asshai, past the Jade Sea and beyond, one can imagine a sort of "grain road" analogous to our own Silk and Spice roads to ship food into western Essos and Westeros. It would certainly be profitable and you wouldn't even need to wait for winter: Any trader with a brain could think of buying up grain all summer to start selling once winter begins.

This doesn't also require particularly long trade routes. It's not like you need a ship going all the way from King's Landing to Asshai, for instance. Going by this map, you can have King's Landing import from Pentos, which creates a food demand in Pentos, causing them to import from Tyrosh, driving prices up there and incentivizing Tyroshi traders to go buy cheaper food from Lys. Lysine traders buy from Volantis, Volantis imports from Ghis, which imports from Qarth, which imports from Yi Ti, which imports from Asshai. At every leg of this long chain, the price jumps a little to account for traders of that city skimming some profit off the top. It would inflate food prices in Westeros somewhat, but then all the unemployed Westerosi farmers who become craftsmen and artisans will also inflate prices of goods, thereby compensating somewhat. Ultimately, once again the market is efficient; both food and goods will be stockpiled and rationed out by arbitragers, and price volatility will be more of a "stupid person who forgot to prepare for the winter" tax. You would think that banks and insurance companies of all sorts would spring up like mushrooms in this environment, but the books don't mention much of them beyond perhaps the Iron Bank (hmm, I wonder how that came about).

Anyhow, in this model, being a naval superpower is wholly unnecessary - although it is clear that the volume of trade will be very large (unlike our silk and spice trades, the trade is also in bulk commodities) so piracy will be a problem. All of these regional powers must therefore have sophisticated coast guard and highway police systems, or at least a developed private security market (that would actually explain the multitude of mercenary companies in Essos). All of these can of course be paid for with previously mentioned trade profits (tariffs and tax if state security, and wider profit margins if private).

Not all trade need go through the sea. For example the area around Valyria is supposed to be dangerous to navigate - trade can take a detour through a highway for land caravans.

Conclusion

Martin's universe seems like, in many ways, "medieval Europe with a few twists". In our world these problems of seasonal food security have been solved in many ways, I don't see how Westeros is qualitatively different such that similar solutions cannot be applied.

However, I think he made some of the twists a bit too consequential - for instance the multi year seasons, in my opinion, would necessarily create an environment far more different from our world than is shown. There is some ambiguity whether the world has always been this way, or if this is the result of some magic spell or supernatural catastrophe connected to the Doom of Valyria, but in either case there would be dramatic consequences beyond what has been shown.

Since these consequences have not been shown, their absence has not been explained, much of the world's functioning is shrouded in deliberate mystery (for instance it is often assumed that Westeros lies on a spherical planet similar to ours, but even this has not really been definitively confirmed - for all we know it could be some weird ringworld or magical infinite plane), so we cannot really drill down to the nuts and bolts and definitively "demonstrate" how they survive the winter in the way you attempt. The best we can do is speculate, as far as I can see along the following lines:

Conditions in the long winter are about the same as conditions in our short winter (eg. wild game animals somehow do not starve), so they would overcome it in ways similar to how we overcome our winter, with similar consequences to what was seen in our history. (the obvious and most likely case)

Conditions in the long winter must differ fundamentally from our short winters, and survival requires radically different approaches than how we survive our winters, and we cannot predict these approaches since it has not been made clear exactly how the long winter differs. (especially if you follow my reasoning that such a long winter would have serious evolutionary, ecological, cultural and economic consequences)

They will not survive the winter (but then what about the past ones?).

They will be shown to survive the winter in a fundamentally unrealistic fashion (not the first time a fantasy book has done it, after all).

They will be shown to survive it but not how, so we will never know.

I am personally skeptical that the series will be finished, because of Martin's past record, so my prediction is that the sixth book, along with private notes which will end up being published in the far future, will hint at something between 1 and 2, and ultimately we will be left with 2, meanwhile Martin has been planning something like 1 (with some twists).

Re: children, I imagine many people would decline to have children in the winter for that very reason.
– Azor AhaiJun 26 '16 at 2:22

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@Azor-Ahai Or they might time it so that the child is old enough to help with farming (so they can maximize the production they get from their summer) once the winter is over, or perhaps being indoors all the time with nothing else to do makes conception more likely.
– SuperbestJun 26 '16 at 2:39

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"should lead to the evolution of many more cold-tolerant microbes" - for refrigeration you'd be right, but below-freezing temperature is probably a gap that non-extremophile bacteria can't bridge. Surviving is one thing, breeding in such temperatures is quite another.
– Random832Jun 26 '16 at 18:36

1

@Random832 There are microbes that can live below freezing - they're called psychrophiles. For instance Psychrobacter is a bacteria that can apparently grow in -10C.
– SuperbestJun 26 '16 at 18:42

Great answers have been given so far, I would like to add what GRRM had to say on the matter himself. It mostly confirms what has already been given in the existing answers, but it always nice to see "word-of-god". Although I am not sure of the identity of the person asking the questions, the interview comes from the So Spake Martin archives on Westeros.org. The original interview was done on June 21, 2001.

[Writer] I'd like to greet you on behalf of our group of Russian fans of your work, and to thank you sincerely for your wonderful books. Special thanks from me personally, as a great lover of Medieval history and lore - it is so rare a thing to see such a beautiful and vivid image of Medieval world in literature. Thank you again:).

[GRRM] You're most welcome. I appreciate the kind words. Are you reading the books in English or in Russian? In either case, I am glad you're enjoying them.

[Writer] But I'd also like to ask you a couple of questions - of course, if it doesn't take away too much time and attention. The first and main of these questions we've been discussing for some time now, and weren't able to come to a clear answer by ourselves. It's the question of agriculture in the North. From what we've seen in the books so far, it looks like even in summer the snow covers most of the lands in the North, and it surely does cover all in winter, doesn't it?

[GRRM] I wouldn't say that snow "covers most of the lands" in summer. Rather than they have occasional summer snows. It never gets really hot in the north, even in summer, but it's not icy and snowing all the time either. Winter is a different tale.

[Writer] But quite a lot of people are living there. What do they eat?

[GRRM] A lot of food is stored. Smoked, salted, packed away in granaries, and so on. The populations along the coast depend on fishing a great deal, and even inland, there is ice fishing on the rivers and on Long Lake. And some of the great lords try and maintain greenhouses to provide for their own castles... the "glass gardens" of Winterfell are referred to several times.

But the short answer is... if the winter lasts too long, the food runs out... and then people move south, or starve...

[Writer] Are there some areas without snow, which are suitable for agriculture, or are there significant temperature changes inside the "bigger seasons"? To grow a harvest, at least a couple of months' time of warm temperature (15-20 degrees by Celsius) is needed. Is it available in the North?

[GRRM] Sometimes. It is not something that can be relied on, given the random nature of the seasons, but there are "false springs" and "spirit summers." The maesters try and monitor temperature grand closely, to advise on when to plant and when to harvest and how much food to store.